Polymer compound, positive resist composition, and method of forming resist pattern

ABSTRACT

There is provided a positive resist composition including a resin component (A) which displays increased solubility in an alkali developing solution under action of acid, and an acid generator component (B) which generates an acid upon exposure, wherein the resin component (A) includes a polymer compound (A1) containing a structural unit (a0) represented by a general formula (a0-1) shown below, and a structural unit (a1) derived from an acrylate ester which has an acid dissociable, dissolution inhibiting group: 
     
       
         
         
             
             
         
       
     
     (in the formula (a0-1), R represents a hydrogen atom, a lower alkyl group, or a halogenated lower alkyl group; two of R′ each independently represents a hydrogen atom, a lower alkyl group, or an alkoxy group of 1 to 5 carbon atoms; X represents an alkylene group of 1 to 5 carbon atoms, an oxygen atom, or a sulfur atom.).

TECHNICAL FIELD

The present invention relates to a polymer compound, a positive resistcomposition, and a method of forming a resist pattern.

This application claims priority from Japanese Patent Application No.2007-233247 filed on Sep. 7, 2007, the disclosure of which isincorporated by reference herein.

BACKGROUND ART

Lithography techniques include processes in which, for example, a resistfilm formed from a resist material is formed on top of a substrate, theresist film is selectively exposed with irradiation such as light, anelectron beam or the like through a mask in which a predeterminedpattern has been formed, and then a developing treatment is conducted,thereby forming a resist pattern of the prescribed shape in the resistfilm. Resist materials in which the exposed portions change to becomesoluble in a developing liquid are termed positive materials, whereasresist materials in which the exposed portions change to becomeinsoluble in the developing liquid are termed negative materials.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength of the exposure light source. Conventionally, ultravioletradiation typified by g-line and i-line radiation has been used, butnowadays KrF excimer lasers and ArF excimer lasers are starting to beintroduced in mass production of semiconductor elements. Furthermore,research is also being conducted into lithography techniques that use F2excimer lasers, electron beams (EB), extreme ultraviolet radiation (EUV)and X-rays.

Resist materials are required to have lithography properties such ashigh sensitivity to the aforementioned light source and enoughresolution to reproduce patterns with very fine dimensions. As resistmaterials which fulfill the aforementioned requirements, there is used achemically-amplified resist containing a base resin that displayschanged alkali solubility under action of acid, and an acid generatorthat generates acid upon exposure. For example, a chemically-amplifiedpositive resist includes a resin in which the alkali solubilityincreases under action of an acid as a base resin and an acid generator,and when an acid is generated from the acid generator upon exposure inthe formation of a resist pattern, the exposed portions are converted toa soluble state in an alkali developing solution.

Until recently, polyhydroxystyrene (PHS) or derivative resins (PHS-basedresins) in which the hydroxyl groups have been protected with aciddissociable, dissolution inhibiting groups, which exhibit a high degreeof transparency relative to KrF excimer laser (248 nm), have been usedas the base resin of chemically-amplified resists. However, becausePHS-based resins contain aromatic rings such as benzene rings, theirtransparency is inadequate for light with a wavelength shorter than 248nm, such as light of 193 nm. Accordingly, chemically-amplified resiststhat use a PHS-based resin as the base resin have a disadvantage in thatthey have low resolution in processes that use, for example, light of193 nm.

As a result, resins (acrylic resins) that contain structural unitsderived from (meth)acrylate esters within the main chain are now widelyused as base resins for resists in ArF excimer laser lithography and thelike, as they exhibit excellent transparency in the vicinity of 193 nm(for example, see Patent Document 1).

Here, the term “(meth)acrylate ester” is a generic term that includeseither or both of the acrylate ester having a hydrogen atom bonded withthe α-position and the methacrylate ester having a methyl group bondedwith the α-position. The term “(meth)acrylate” is a generic term thatincludes either or both of the acrylate having a hydrogen atom bondedwith the α-position and the methacrylate having a methyl group bondedwith the α-position. The term “(meth)acrylic acid” is a generic termthat includes either or both of the acrylic acid having a hydrogen atombonded with the α-position and the methacrylic acid having a methylgroup bonded with the α-position.

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2003-241385.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In recent years, as the miniaturization of the resist pattern hasprogressed more and more, it is strongly expected to develop a positiveresist composition with even better resolution and sensitivity, whilekeeping excellent lithography properties.

The present invention takes the above circumstances into consideration,with an object of providing a polymer compound with excellent resolutionand sensitivity, suitable for a positive resist composition, a positiveresist composition which includes the polymer compound, and a method offorming a resist pattern.

Means for Solving the Problems

The inventors of the present invention suggest the following in order toresolve the above problem.

A first aspect of the present invention is a polymer compound includinga structural unit (a0) represented by a general formula (a0-1) shownbelow, and a structural unit (a1) derived from an acrylate ester whichcontains an acid dissociable, dissolution inhibiting group.

(in the formula (a0-1), R represents a hydrogen atom, a lower alkylgroup, or a halogenated lower alkyl group; two of R′ each independentlyrepresents a hydrogen atom, a lower alkyl group, or an alkoxy group of 1to 5 carbon atoms; and X represents an alkylene group of 1 to 5 carbonatoms, an oxygen atom, or a sulfur atom.).

A second aspect of the present invention is a positive resistcomposition including a resin component (A) which displays increasedsolubility in an alkali developing solution under action of acid, and anacid generator component (B) which generates an acid upon exposure,wherein the resin component (A) contains a polymer compound (A1) whichcontains the structural unit (a0) represented by the general formula(a0-1), and the structural unit (a1) derived from an acrylate esterwhich contains an acid dissociable, dissolution inhibiting group.

A third aspect of the present invention is a method of forming a resistpattern which includes forming a positive resist composition on asubstrate using a positive resist composition described in the secondaspect of the present invention; conducting exposure of the resist film;and developing the resist film with an alkali to form a resist pattern.

Here, the term “structural unit” represents a monomer unit thatcontributes to the formation of a resin component (polymer).

The term “exposure” is used as a general concept involving irradiationwith any form of radiation.

The term “alkyl group” is a concept containing a linear, branched andcyclic monovalent saturated hydrocarbon group, unless another definitionis particularly provided.

The term “lower alkyl group” represents an alkyl group of 1 to 5 carbonatoms.

EFFECTS OF THE INVENTION

The present invention provides a polymer compound with an excellentresolution and sensitivity, a positive resist composition which includesthe polymer compound; and a method of forming a resist pattern.

BEST MODE FOR CARRYING OUT THE INVENTION <<Polymer Compound>>

The polymer compound of the present invention contains a structural unit(a0) represented by the general formula (a0-1), and a structural unit(a1) derived from an acrylate ester containing an acid dissociable,dissolution inhibiting group.

Structural Unit (a0)

The structural unit (a0) is a structural unit represented by a generalformula (a0-1) shown below.

(in the formula (a0-1), R represents a hydrogen atom, a lower alkylgroup, or a halogenated lower alkyl group; two of R′ each independentlyrepresents a hydrogen atom, a lower alkyl group, or an alkoxy group of 1to 5 carbon atoms; and X represents an alkylene group of 1 to 5 carbonatoms, an oxygen atom, or a sulfur atom.).

In the formula (a0-1), R represents a hydrogen atom, a lower alkylgroup, or a halogenated lower alkyl group. Specific examples of thelower alkyl group for R include linear or branched lower alkyl groupssuch as a methyl group, an ethyl group, a propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, a tert-butyl group, a pentylgroup, an isopentyl group, and a neopentyl group. R is preferably ahydrogen atom or a methyl group, and more preferably a methyl group.

Two of R′ each independently represents a hydrogen atom, a lower alkylgroup, or an alkoxy group of 1 to 5 carbon atoms. A lower alkyl groupfor R′ is the same as the lower alkyl group for R. Examples of thealkoxy group of 1 to 5 carbon atoms for R′ include a methoxy group, anethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxygroup, and a tert-butoxy group. R′ is preferably a hydrogen atom, interms of industrial availability.

The structural unit (a0) can be used alone, or in combinations of two ormore different units.

Specific examples of structural units (a0) represented by the abovegeneral formula (a0-1) are shown below. The structural unit (a0) ispreferably a structural unit represented by a general formula (a0-1-1)shown below.

X represents an alkylene group of 1 to 5 carbon atoms, an oxygen atom,or a sulfur atom. Examples of the alkylene group of 1 to 5 carbon atomsfor X include linear or branched lower alkylene groups such as amethylene group, an ethylene group, a propylene group, dimethylmethylenegroup, and a 1,1-dimethylethylene group. Of these, a methylene group ispreferable.

The proportion of the structural unit (a0) in the polymer compound ispreferably from 5 to 60 mol %, more preferably from 10 to 50 mol %, andstill more preferably from 20 to 50 mol %, relative to the combinedtotal of all the structural units that constitute the polymer compound.When this proportion is not less than the lower limit in the aboverange, then the effect by containing the structural unit (a0) can besufficiently obtained, whereas when the proportion is not more than theupper limit in the above range, a good quantitative balance with theother structural units can be attained.

The monomer which derives the structural unit (a0) represented by thegeneral formula (a0-1) is represented by a general formula (a0-0-1)shown below. Here, in the general formula (a0-0-1), R, two of R′, and Xare the same as R, two of R′, and X in the formula (a0-1).

(in the formula (a0-0-1), R, two of R′, and X are the same as R, two ofR′, and X in the formula (a0-1)).

The monomer represented by the general formula (a0-0-1) can bemanufactured, for example, by reacting a (meth)acrylic acid representedby a general formula (q1) shown below, a compound represented by ageneral formula (q2) shown below, and a5-hydroxy-3-oxa-2-thia-tricyclo[4.2.1.0^(4,8)]nonane derivative as anexample in a solvent such as tetrahydrofuran, toluene, and methylenechloride. R in the general formula (q1) and two of R′ and X in thegeneral formula (q2) are the same as R, two of R′, and X in the formula(a0-1).

(in the formula (q1), R is the same as R in the formula (a0-1).)

(in the formula (q2), two of R′ and X are the same as R′ and X in theformula (a0-1).)

The monomer represented by the general formula (a0-0-1) can be obtained,for example, by reacting the compound represented by the general formula(q2) with a reactive derivative of the (meth)acrylic acid represented bythe general formula (q1), such as a (meth)acrylic halide like a(meth)acrylic chloride and a (meth)acrylic anhydride in a solvent, inthe presence of a base such as triethylamine, pyridine, or 4-dimethylaminopyridine, if necessary. Also, it can be obtained by reacting thecompound represented by the general formula (q2) with an ester body ofthe (meth)acrylic acid represented by the general formula (q1) in asolvent, in the presence of a transesterification catalyst such astitanium isopropoxide. Also, it can by obtained by reacting the compoundrepresented by the general formula (q2) with the (meth)acrylic acidrepresented by the general formula (q1) in a solvent, in the presence ofa strong acid such as hydrochloric acid, sulfuric acid, orp-toluenesulfonic acid.

The thus obtained monomer represented by the general formula (a0-0-1)can be separated and purified, for example, by using a separation methodsuch as filtration, concentration, distillation, extraction,crystallization, recrystallization, and column chromatography, or byusing the methods in combination.

The compound represented by the general formula (q2) can be obtained,for example, by a cyclization reaction of a compound represented by ageneral formula (q2-0) shown below.

(in the formula (q2-0), two of R′ and X are the same as two of R′ and Xin the formula (a0-1); R″ represents a hydrogen atom, a lower alkylgroup, a linear, branched, or cyclic lower alkenyl group of 1 to 6carbon atoms, or an aryl group.)

In the general formula (q2-0), two of R′ are the same as two of R′ inthe formula (a0-1).

R″ represents a hydrogen atom, a lower alkyl group, a linear, branched,or cyclic lower alkenyl group of 1 to 6 carbon atoms, and is preferablya hydrogen atom.

The cyclization reaction proceeds, for example, only by dissolving thecompound represented by the formula (q2-0) in a solvent, in the casethat R″ is a hydrogen atom. In the case that R″ is not a hydrogen atom,the cyclization reaction proceeds immediately after the compound inwhich R″ is a hydrogen atom is produced by hydrolyzing the compoundrepresented by the formula (q2-0) using a conventional method such as analkali hydrolysis reaction or an acid hydrolysis reaction, and thus thecompound represented by the formula (q2) is produced. The thus obtainedmonomer represented by the general formula (q2) can be separated andpurified, for example, by using a separation method such as filtration,concentration, distillation, extraction, crystallization,recrystallization, and column chromatography, or by using the methods incombination.

The compound represented by the general formula (q2-0) can be obtained,for example, by using a method disclosed in Japanese Unexamined PatentApplication, First Publication No. 2007-31355.

Structural Unit (a1)

Structural unit (a1) is a structural unit derived from an acrylate esterhaving an acid dissociable, dissolution inhibiting group.

Here, the term “structural unit derived from an acrylate ester” in thepresent specification and claims represents a structural unit formed bycleavage of the ethylenic double bond of an acrylate ester.

The term “acrylate ester” is a concept containing an acrylate ester inwhich a hydrogen atom is bonded with a carbon atom at the α-position,and an α-substituted acrylate ester in which a hydrogen atom bonded witha carbon atom at the α-position is substituted with another substituentgroup (an atom or group other than a hydrogen atom). Examples of thesubstituent group include a lower alkyl group, and a halogenated loweralkyl group.

The term “α-position (carbon atom at the α-position)” in a structuralunit derived from an acrylic acid or an acrylate ester represents acarbon atom with which a carbonyl group is bonded, if not otherwisespecified.

The term “alkyl group” is a concept containing a linear, branched andcyclic monovalent saturated hydrocarbon group, unless another definitionis particularly provided.

The term “lower alkyl group” represents an alkyl group of 1 to 5 carbonatoms.

In the acrylate ester, specific examples of the lower alkyl group as thesubstituent group at the α-position include linear or branched loweralkyl groups such as a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, and a neopentyl group.

In the present invention, the group which is bonded with the α-positionis preferably a hydrogen atom, a lower alkyl group or a halogenatedlower alkyl group, more preferably a hydrogen atom, a lower alkyl groupor a fluorinated lower alkyl group, and still more preferably a hydrogenatom or a methyl group, in terms of industrial availability.

As the acid dissociable, dissolution inhibiting group in the structuralunit (a1), any of the groups that have been proposed as aciddissociable, dissolution inhibiting groups for the base resins ofchemically amplified resists can be used, provided the group has analkali dissolution-inhibiting effect that renders the entire polymercompound alkali-insoluble prior to dissociation, and then followingdissociation by action of acid, causes the entire polymer compound tochange to an alkali-soluble state. Generally, groups that form either acyclic or chain-like tertiary alkyl ester with the carboxyl group of the(meth)acrylic acid, and acetal-type acid dissociable, dissolutioninhibiting groups such as alkoxyalkyl groups are widely known. Here, theterm “(meth)acrylate ester” is a generic term that includes either orboth of the acrylate ester having a hydrogen atom bonded with theα-position and the methacrylate ester having a methyl group bonded withthe α-position.

Here, the term “tertiary alkyl ester” represents a structure in which anester is formed by substituting the hydrogen atom of a carboxyl groupwith a chain-like or cyclic alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic alkyl group is bonded with the oxygenatom at the terminal of the carbonyloxy group (—C(O)—O—). In thetertiary alkyl ester, the bond of the oxygen atom with the tertiarycarbon atom is cleaved by the action of acid.

Here, the chain-like or cyclic alkyl group may contain a substituentgroup.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups include aliphatic branched, acid dissociable,dissolution inhibiting groups and aliphatic cyclic group-containing aciddissociable, dissolution inhibiting groups.

Here, in the present claims and specification, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound or the like that contains no aromaticity.

The term “aliphatic branched” represents a branched structure having noaromaticity. The “aliphatic branched, acid dissociable, dissolutioninhibiting group” is not limited to groups (hydrocarbon groups) composedof carbon atoms and hydrogen atoms, and is preferably a hydrocarbongroup. Further, the “hydrocarbon group” may be either saturated orunsaturated, and is preferably saturated.

Examples of aliphatic branched, acid dissociable, dissolution inhibitinggroups include tertiary alkyl groups of 4 to 8 carbon atoms, andspecific examples include a tert-butyl group, a tert-pentyl group and atert-heptyl group.

The term “aliphatic cyclic group (alicyclic group)” means a monocyclicor polycyclic group which has no aromaticity.

The “aliphatic cyclic group” within the structural unit (a1) may or maynot contain a substituent group. Examples of substituent groups includea lower alkyl group of 1 to 5 carbon atoms, a lower alkoxy group of 1 to5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group of 1 to5 carbon atoms, and an oxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentgroups is not limited to groups (hydrocarbon groups) composed of carbonatoms and hydrogen atoms, and is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,and is preferably saturated. The “aliphatic cyclic group” is preferablya polycyclic group.

Examples of the aliphatic cyclic groups include groups in which one ormore hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane in which a lower alkyl group, a fluorine atom or afluorinated lower alkyl group may or may not be included as asubstituent group. Specific examples include groups in which at leastone hydrogen atom has been removed from a monocycloalkane such ascyclopentane and cyclohexane; and groups in which at least one hydrogenatom has been removed from a polycycloalkane such as adamantane,norbornane, isobornane, tricyclodecane or tetracyclododecane.

As the aliphatic cyclic group-containing acid dissociable, dissolutioninhibiting group, for example, a group which has a tertiary carbon atomon the ring structure of the cycloalkyl group can be mentioned. Specificexamples thereof include 2-methyl-2-adamantyl group and a2-ethyl-2-adamantyl group. Further, in the structural units representedby general formulae (a1″-1) to (a1″-6) shown below, groups bonded withthe oxygen atom of the carbonyloxy group (—C(O)—O—), that is, groupshaving an aliphatic cyclic group such as an adamantyl group, acyclohexyl group, a cyclopentyl group, a norbornyl group, atricyclodecanyl group or a tetracyclodecanyl group, and a branchedalkylene group having a tertiary carbon atom bonded thereto, can beexemplified.

(wherein, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; and R¹⁵ and R¹⁶ each independentlyrepresents an alkyl group (which may be linear or branched, and ispreferably an alkyl group of 1 to 5 carbon atoms).)

In the general formulae (a1″-1) to (a1″-6), the lower alkyl group orhalogenated lower alkyl group for R are the same as the lower alkylgroup or halogenated lower alkyl group which can be bonded with theα-position of the aforementioned acrylate ester.

An “acetal-type acid dissociable, dissolution inhibiting group”generally replaces a hydrogen atom at the terminal of an alkali-solublegroup such as a carboxy group or a hydroxyl group, so as to be bondedwith an oxygen atom. When acid is generated upon exposure, the generatedacid acts to break the bond between the acetal-type acid dissociable,dissolution inhibiting group and the oxygen atom with which theacetal-type, acid dissociable, dissolution inhibiting group is bonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groupsinclude groups represented by a general formula (p1) shown below.

(wherein, R¹′ and R²′ each independently represents a hydrogen atom or alower alkyl group; n represents an integer of 0 to 3; and Y represents alower alkyl group or an aliphatic cyclic group.)

In the above formula, n is preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 0.

The lower alkyl group for R¹′ or R²′ is the same as the lower alkylgroups described above in R. As the lower alkyl group of R¹′ or R²′, amethyl group or an ethyl group is preferable, and a methyl group is mostpreferable.

In the present invention, at least one of R¹′ and R²′ is preferably ahydrogen atom. That is, it is preferable that the acid dissociable,dissolution inhibiting group (p1) be a group represented by a generalformula (p1-1) shown below.

(wherein, R¹′, n, and Y are as defined above.)

The lower alkyl group for Y is the same as the lower alkyl groupdescribed above in R.

As the aliphatic cyclic group for Y, any of the aliphatic monocyclic orpolycyclic groups which have been proposed for conventional ArF resistsand the like can be used by being appropriately selected from those. Forexample, the same groups described above in the “aliphatic cyclic group”can be exemplified.

Further, as the acetal-type, acid dissociable, dissolution inhibitinggroup, groups represented by general formula (p2) shown below can alsobe exemplified.

(wherein R¹⁷ and R¹⁸ each independently represents a linear or branchedalkyl group or a hydrogen atom; and R¹⁹ represents a linear, branched orcyclic alkyl group. Alternately, R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, wherein the terminal ofR¹⁷ may be bonded with the terminal of R¹⁹ thereby forming a ring.)

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly preferable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ormethyl group, and most preferably an ethyl group.

When R¹⁹ represents a cyclic alkyl group, it preferably has 4 to 15carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably5 to 10 carbon atoms. Specific examples of the cyclic alkyl groupinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, in which a fluorine atom or afluorinated alkyl group may or may not be included as a substituentgroup. Specific examples thereof include groups in which one or morehydrogen atoms have been removed from a monocycloalkane such ascyclopentane and cyclohexane, and a polycycloalkane such as adamantane,norbornane, isobornane, tricyclodecane, and tetracyclododecane. Ofthese, a group in which one or more hydrogen atoms have been removedfrom adamantane is preferable.

In the general formula (p2), R¹⁷ and R¹⁹ may each independentlyrepresents a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bondedwith the terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomwith which R¹⁹ is bonded, and the carbon atom with which the oxygen atomand R¹⁷ are bonded. Such a cyclic group is preferably a 4- to 7-memberedring, and more preferably a 4- to 6-membered ring. Specific examples ofthe cyclic group include a tetrahydropyranyl group and atetrahydrofuranyl group.

As the structural unit (a1), it is preferable to use at least one memberselected from the group consisting of structural units represented by ageneral formula (a1-0-1) shown below and structural units represented bya general formula (a1-0-2) shown below.

(wherein, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; and X¹ represents an acid dissociable,dissolution inhibiting group.)

(wherein, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; X² represents an acid dissociable,dissolution inhibiting group; and Y² represents an alkylene group or analiphatic cyclic group.)

In the general formula (a1-0-1), the lower alkyl group or halogenatedlower alkyl group of R are the same as the lower alkyl group orhalogenated lower alkyl group which can be bonded with the α-position ofthe aforementioned acrylate ester.

X¹ is not particularly limited as long as it is an acid dissociable,dissolution inhibiting group. Examples thereof include theaforementioned tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups and acetal-type acid dissociable, dissolutioninhibiting groups, and tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups are preferable.

In the general formula (a1-0-2), R is the same as those described above.

X² is the same as X¹ described in the general formula (a1-0-1).

Y² is preferably an alkylene group of 1 to 10 carbon atoms or a bivalentaliphatic cyclic group. As the aliphatic cyclic group, the same as thosedescribed in “aliphatic cyclic group” can be used, with the exceptionthat two or more hydrogen atoms are removed.

When Y² represents an alkylene group of 1 to 10 carbon atoms, it is morepreferable that the number of carbon atoms be 1 to 6, still morepreferably 1 to 4, and most preferably 1 to 3.

When Y² represents a divalent aliphatic cyclic group, it is particularlypreferable that the divalent aliphatic cyclic group be a group in whichtwo or more hydrogen atoms have been removed from a cyclopentane, acyclohexane, a norbornane, an isobornane, an adamantane, atricyclodecane or a tetracyclododecane.

(wherein X′ represents a tertiary alkyl ester-type acid dissociable,dissolution inhibiting group; Y represents a lower alkyl group of 1 to 5carbon atoms or an aliphatic cyclic group; n represents an integer of 0to 3; Y² represents an alkylene group or an aliphatic cyclic group; R isas defined above; and R¹′ and R²′ each independently represents ahydrogen atom or a lower alkyl group of 1 to 5 carbon atoms.)

In the formula, X′ is the same as a tertiary alkyl ester-type aciddissociable, dissolution inhibiting group described in X¹.

R¹′, R²′, n, and Y are the same as R¹′, R²′, n, and Y in the generalformula (p1) shown in “acetal-type acid dissociable, dissolutioninhibiting group”.

Y² is the same as Y² in the general formula (a1-0-2).

Specific examples of structural units represented by the generalformulae (a1-1) and (a1-4) shown above include the following.

The structural unit (a1) can be used alone, or in combinations of two ormore different units.

Among these, structural units represented by the general formula (a1-1)are preferable. More specifically, at least one structural unit selectedfrom the group consisting of structural units represented by theformulae (a1-1-1) to (a1-1-6) and (a1-1-35) to (a1-1-41) is morepreferable.

Further, as the structural unit (a1), structural units represented by ageneral formula (a1-1-01) shown below which includes the structuralunits represented by formulae (a1-1-1) to (a1-1-4), and structural unitsrepresented by a general formula (a1-1-02) shown below which includesthe structural units represented by formulae (a1-1-35) to (a1-1-41) arealso preferable.

(wherein, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; and R¹¹ represents a lower alkyl group.)

(wherein, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R¹² represents a lower alkyl group; and hrepresents an integer of 1 to 3.)

In the general formula (a1-1-01), R is as defined above. The lower alkylgroup for R¹¹ is the same as the lower alkyl group described above in R,and is preferably a methyl group or an ethyl group.

In the general formula (a1-1-02), R is as defined above. The lower alkylgroup for R¹² is the same as the lower alkyl group described above in R.R¹² is preferably a methyl group or an ethyl group, and most preferablyan ethyl group. h is preferably 1 or 2, and most preferably 2.

The proportion of the structural unit (a1) in the polymer compound ofthe present invention is preferably from 10 to 80 mol %, more preferablyfrom 20 to 70 mol %, and still more preferably from 25 to 50 mol %,relative to the combined total of all the structural units thatconstitute the polymer compound. When this proportion is not less thanthe lower limit in the above range, then the effect by containing thestructural unit (a1) can be sufficiently obtained, whereas when theproportion is not more than the upper limit in the above range, a goodquantitative balance with the other structural units can be attained.

Structural Unit (a3)

The polymer compound of the present invention preferably contains astructural unit (a3) derived from an acrylate ester which has a polargroup-containing aliphatic hydrocarbon group, in addition to thestructural units (a0) and (a1).

Examples of the polar group include a hydroxyl group, a cyano group, acarboxyl group, a hydroxyalkyl group in which a part of the hydrogenatoms in an alkyl group is substituted with fluorine atoms. Of these, ahydroxyl group is particularly preferable.

Examples of the aliphatic hydrocarbon group include a linear or branchedhydrocarbon group of 1 to 10 carbon atoms (preferably an alkylenegroup), and a polycyclic aliphatic hydrocarbon group (polycyclic group).The polycyclic group can be appropriately selected from the multitude ofstructural units proposed as resins in resist compositions for ArFexcimer lasers and the like. The polycyclic group preferably has 7 to 30carbon atoms.

Of these, a structural unit derived from an acrylate ester having thepolycyclic aliphatic group which contains a hydroxyl group, cyano group,a carboxyl group, or a hydroxyalkyl group in which a part of thehydrogen atoms within an alkyl group has been substituted with fluorineatoms is more preferable. Examples of the polycyclic group includegroups in which two or more hydrogen atoms have been removed from abicycloalkane, a tricycloalkane, a tetracycloalkane, or the like.Specific examples include a group in which two or more hydrogen atomshave been removed from a polycycloalkane such as an adamantane, anorbornane, an isobornane, a tricyclodecane, or a tetracyclododecane. Ofthese polycyclic groups, a group in which two or more hydrogen atomshave been removed from an adamantane, a norbornane, or atetracyclododecane is industrially preferable.

As the structural unit (a3), for example, a structural unit derived froma hydroxyethyl ester of acrylic acid is preferable, when the hydrocarbongroup within the polar group-containing aliphatic hydrocarbon group is alinear or branched hydrocarbon group of 1 to 10 carbon atoms. On theother hand, a structural unit represented by a general formula (a3-1),(a3-2), or (a3-3) is preferable, when the hydrocarbon group is apolycyclic group.

(wherein, R represents the same as defined above; j represents aninteger of 1 to 3; k represents an integer of 1 to 3; t′ represents aninteger of 1 to 3; 1 represents an integer of 1 to 5; and s representsan integer of 1 to 3.)

In the general formula (a3-1), j is preferably 1 or 2, and morepreferably 1. In the case that j is 2, a structural unit in which ahydroxyl group is bonded with the 3-position and 5-position of theadamantyl group is preferable. In the case that j is 1, a structuralunit in which a hydroxyl group is bonded with the 3-position of theadamantyl group is preferable.

Of these, it is preferable that j be 1, and the hydroxyl group be bondedwith the 3-position of the adamantyl group.

In the general formula (a3-2), k is preferably 1. In the general formula(a3-2), a structural unit in which a cyano group is bonded with the5-position or 6-position of the norbornyl group is preferable.

In the general formula (a3-3), V is preferably 1. I is preferably 1. sis preferably 1. Further, in the general formula (a3-3), it ispreferable that a 2-norbornyl group or 3-norbornyl group be bonded atthe terminal of the carboxy group of the acrylic acid. It is preferablethat a fluorinated alkyl alcohol be bonded with the 5-position or6-position of the norbornyl group.

The structural unit (a3) can be used alone, or in combinations of two ormore different units.

The proportion of the structural unit (a3) in the polymer compound ofthe present invention is preferably from 5 to 50 mol %, more preferablyfrom 5 to 40 mol %, and still more preferably from 5 to 25 mol %,relative to the combined total of all the structural units thatconstitute the polymer compound.

The polymer compound of the present invention may contain structuralunits other than the structural units (a0), (a1), and (a3). Such astructural unit is, for example, a structural unit (a2) or (a4)described below.

Also, the polymer compound of the present invention can be obtained, forexample, by a conventional radical polymerization or the like of themonomers that give rise to each of the structural units, using a radicalpolymerization initiator such as azobisisobutyronitrile (AIBN).

The polymer compound of the present invention contains a structural unit(a0) represented by the general formula (a0-1), and a structural unit(a1) derived from an acrylate ester containing an acid dissociable,dissolution inhibiting group. As described below, since the polymercompound of the present invention contains the structural unit (a0)represented by the general formula (a0-1), excellent chemical stabilityand hydrolyzability can be obtained, and thus the polymer compound cansuitably be used as a material for a positive resist.

<<Positive Resist Composition>>

A positive resist composition of the present invention includes a resincomponent (A) which displays increased solubility in an alkalideveloping solution under action of acid, and an acid generatorcomponent (B) which generates an acid upon exposure, wherein the resincomponent (A) contains a polymer compound (A1) which contains thestructural unit (a0) represented by the general formula (a0-1) and thestructural unit (a1) derived from an acrylate ester which contains anacid dissociable, dissolution inhibiting group.

In the positive resist composition of the present invention, thecomponent (A) is insoluble in an alkali developing solution beforeexposure. When the acid generated from the component (B) upon exposureacts on the component (A), the acid dissociable, dissolution inhibitinggroups are dissociated, and the solubility of the entire component (A)in an alkali developing solution is enhanced. As a result, the positiveresist composition changes from an alkali-insoluble state to analkali-soluble state.

Therefore, in the formation of a resist pattern, when a resist filmobtained by using the positive resist composition is subjected toselective exposure, the exposed area becomes soluble in an alkali, whilethe unexposed area remains alkali-insoluble, and hence a resist patterncan be formed by developing with an alkali.

<Component (A)>

In the present invention, the component (A) includes the polymercompound (A1) containing the structural unit (a0) represented by thegeneral formula (a0-1) and the structural unit (a1) derived from anacrylate ester which contains an acid dissociable, dissolutioninhibiting group.

Structural Unit (a0)

The structural unit (a0) included in the polymer compound (A1) is astructural unit represented by the general formula (a0-1), and is thesame as those described in the polymer compound of the first aspect ofthe present invention.

The structural unit (a0) can be used alone, or in combinations of two ormore different units.

As the structural unit (a0), it is preferable to use at least onestructural unit selected from the group consisting of the generalformulae (a0-1-1) to (a0-1-22), and it is more preferable to use thestructural unit represented by the general formula (a0-1-1).

The proportion of the structural unit (a0) in the polymer compound (A1)is preferably from 5 to 60 mol %, more preferably from 10 to 50 mol %,and still more preferably from 20 to 50 mol %, relative to the combinedtotal of all the structural units that constitute the polymer compound(A1). When this proportion is not less than the lower limit in the aboverange, then the effect by containing the structural unit (a0) can besufficiently obtained, whereas when the proportion is not more than theupper limit in the above range, a good quantitative balance with theother structural units can be attained.

Structural Unit (a1)

The structural unit (a1) included in the polymer compound (A1) is astructural unit derived from an acrylate ester which contains an aciddissociable, dissolution inhibiting group, and is the same as thosedescribed in the polymer compound of the first aspect of the presentinvention.

The structural unit (a1) can be used alone, or in combinations of two ormore different units.

As the structural unit (a1), it is preferable to use at least onestructural unit selected from the group consisting of the generalformulae (a1-1-1) to (a1-1-6) and (a1-1-35) to (a1-1-41), and it is morepreferable to use the structural unit represented by the general formula(a1-1-3).

The proportion of the structural unit (a1) in the polymer compound (A1)is preferably from 10 to 80 mol %, more preferably from 20 to 70 mol %,and still more preferably from 25 to 50 mol %, relative to the combinedtotal of all the structural units that constitute the polymer compound(A1). When this proportion is not less than the lower limit in the aboverange, then a pattern can be easily formed using a positive resistcomposition which includes the structural unit (a1), whereas when theproportion is not more than the upper limit in the above range, a goodquantitative balance with the other structural units can be attained.

Structural Unit (a3)

Further, the polymer compound (A1) preferably contains a structural unit(a3), in addition to the structural units (a0) and (a1). Here, thestructural unit (a3) is a structural unit derived from an acrylate esterwhich has a polar-group containing aliphatic hydrocarbon group, and isthe same as those described in the polymer compound of the first aspectof the present invention.

The structural unit (a3) can be used alone, or in combinations of two ormore different units.

In the polymer compound (A1), the proportion of the structural unit (a3)is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, and stillmore preferably 5 to 25 mol %, relative to the combined total of all thestructural units that constitute the polymer compound (A1).

Structural Unit (a2)

Furthermore, the polymer compound (A1) may contain a structural unit(a2) derived from an acrylate ester which contains a lactone-containingcyclic group, in addition to the structural units (a0) and (a1).

Here, the term “lactone-containing cyclic group” represents a cyclicgroup containing a single ring (lactone ring) which has a “—O—C(O—)”structure. This lactone ring is counted as the first ring, and groupsthat contain only the lactone ring are referred to as monocyclic groups,whereas groups that also contain other ring structures are described aspolycyclic groups regardless of the structure of the other rings.

In the case of using the copolymer (A1) to form a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectiveat improving the adhesion between the resist film and a substrate, andimproving compatibility with the developing solution.

The structural unit (a2) can be used arbitrarily without any particularrestriction.

Specific examples of the lactone-containing monocyclic group include agroup wherein one hydrogen atom is eliminated from γ-butyrolactone.Furthermore, specific examples of the lactone-containing polycyclicgroup include a group wherein one hydrogen atom is eliminated from abicycloalkane, a tricycloalkane, or a tetracycloalkane which contains alactone ring.

Specific examples of the structural unit (a2) include structural unitsrepresented by the general formulae (a2-1) to (a2-5) shown below.

(wherein, R represents a hydrogen atom, a lower alkyl group, or ahalogenated lower alkyl group; R′ represents a hydrogen atom, a loweralkyl group, an alkoxy group of 1 to 5 carbon atoms, or the group of—COOR″; R″ in —COOR″ for R′ represents a hydrogen atom, or a linear,branched, or cyclic alkyl group of 1 to 15 carbon atoms; m represents aninteger of 0 or 1; and A″ represents an alkylene group of 1 to 5 carbonatoms or an oxygen atom.)

R in the general formula (a2-1) to (a2-5) is the same as R describedabove in the structural unit (a1).

The lower alkyl group for R′ is the same as the lower alkyl group for Rin the structural unit (a1).

In the case that R″ is a linear or branched alkyl group, the number ofcarbon atoms is preferably 1 to 10, and more preferably 1 to 5.

In the case that R″ is a cyclic alkyl group, the number of carbon atomsis preferably 3 to 15, more preferably 4 to 12, and most preferably 5 to10. Specific examples of the cyclic alkyl group include groups in whichone or more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, in which a fluorine atom or a fluorinated alkyl groupmay or may not be included as a substituent group. Specific examplesthereof include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane, anda polycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane, and tetracyclododecane.

Specific examples of the alkylene group of 1 to 5 carbon atoms for A″include a methylene group, an ethylene group, an n-propylene group, andan isopropylene group.

In the general formula (a2-1) to (a2-5), R′ is preferably a hydrogenatom in terms of industrial availability.

Specific examples of the structural units represented by the generalformulae (a2-1) to (a2-5) include the following.

In the polymer compound (A1), the structural unit (a2) can be usedalone, or in combination of two or more different units.

The structural unit (a2) is preferably at least one kind selected fromthe group consisting of the structural units represented by the generalformulae (a2-1) to (a2-5), and more preferably at least one kindselected from the group consisting of the structural units representedby the general formulae (a2-1) to (a2-3). Of these, at least one kindselected from the group consisting of the structural units representedby the general formulae (a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2),(a2-3-1), (a2-3-2), (a2-3-9), and (a2-3-10) is particularly preferable.

In the case of containing the structural unit (a2) in the polymercompound (A1), the proportion of the structural unit (a2) in the polymercompound (A1) is preferably 5 to 60 mol %, more preferably 10 to 50 mol%, and still more preferably 20 to 50 mol %, relative to the combinedtotal of all the structural units that constitute the polymer compound(A1) When this proportion is not less than the lower limit in the aboverange, then the effect by containing the structural unit (a2) can besufficiently obtained. When the proportion is not more than the upperlimit in the above range, a good quantitative balance with the otherstructural units can be attained.

Structural Unit (a4)

The polymer compound (A1) may also include a structural unit (a4) otherthan the structural units (a0), (a1), (a2) and (a3), within the rangethat the effect of the present invention is not impaired.

As the structural unit (a4), any other structural unit which cannot beclassified as one of the above structural units (a0) to (a3) can be usedwithout any particular limitations, and any of the multitude ofconventional structural units used within resist resins for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

The structural unit (a4) is preferably, for example, a structural unitderived from an acrylate ester containing a non-acid-dissociablealiphatic polycyclic group. Examples of the polycyclic group include thesame groups described above in the structural unit (a1), and any of themultitude of conventional polycyclic groups used within the resincomponent of resist compositions for ArF excimer lasers or KrF excimerlasers (and preferably for ArF excimer lasers) can be used.

In particular, at least one group selected from amongst atricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group,an isobornyl group, and a norbornyl group is preferable in terms ofindustrial availability and the like. These polycyclic groups maycontain a linear or branched alkyl group of 1 to 5 carbon atoms as asubstituent group.

Specific examples of the structural unit (a4) include a structural unitrepresented by general formulae (a4-1) to (a4-5) shown below.

(wherein, R is as defined above.)

In the case of containing the structural unit (a4) in the polymercompound (A1), the proportion of the structural unit (a4) in the polymercompound (A1) is preferably 1 to 30 mol %, more preferably 10 to 20 mol%, relative to the combined total of all the structural units thatconstitute the polymer compound (A1)

In the present invention, the polymer compound (A1) preferably containsthe structural units (a0), (a1), and (a3), and examples thereof includea polymer compound consisting of the structural units (a0), (a1), and(a3); a polymer compound consisting of the structural units (a0), (a1),(a2), and (a3); a polymer compound consisting of the structural units(a0), (a1), (a3), and (a4); and a polymer compound consisting of thestructural units (a0), (a1), (a2), (a3), and (a4).

As the polymer compound (A1) in the component (A), one kind can be usedalone, or two or more kinds can be used in combination.

In the present invention, it is particularly preferable that the polymercompound (A1) contain structural units shown below in combination.

(in the formula, R and R′ are the same as R and R′ in the generalformula (a0-1), and a plurality of R or R′ may mutually be the same ordifferent; R¹¹ is the same as R″ in the general formula (a1-1-01).)

The polymer compound (A1) can be obtained, for example, by aconventional radical polymerization or the like of the monomerscorresponding with each of the structural units, using a radicalpolymerization initiator such as azobisisobutyronitrile (AIBN).

Also, in the polymer compound (A1), by simultaneously using a chaintransfer agent such as HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH during the abovepolymerization, a —C(CF₃)₂—OH group can be introduced at the terminalsof the polymer compound (A1). When a hydroxyalkyl group in which a partof the hydrogen atoms of the alkyl group has been substituted withfluorine atoms is introduced into a copolymer in this manner, thecopolymer thus obtained can have an advantageous effect in reducing thelevels of developing defects and LER (line edge roughness: non-uniformirregularities within the line side walls).

There is no particular restriction on the weight average molecularweight (Mw) (the polystyrene equivalent value determined by gelpermeation chromatography (GPC), hereinafter defined as the same) of thepolymer compound (A1), and the weight average molecular weight of thepolymer compound (A1) is preferably from 2,000 to 50,000, morepreferably from 3,000 to 30,000, and most preferably from 5,000 to20,000. By ensuring that the weight average molecular weight of thepolymer compound (A1) is no more than the upper limit, solubilitysufficient for a resist relative to a resist solvent can be obtained. Byensuring that it is no less than the lower limit, excellent dry-etchingresistance and excellent sectional shape of the resist pattern can beobtained.

Furthermore, the dispersion degree (Mw/Mn) is preferably within a rangefrom 1.0 to 5.0, more preferably from 1.0 to 3.0, and most preferablyfrom 1.2 to 2.5. Herein, Mn represents the number average molecularweight

<Component (B)>

There is no particular restriction on the component (B), and thoseproposed as acid generators for conventional chemically-amplifiedresists can be used. Examples of these acid generators are numerous, andinclude onium salt-based acid generators such as iodonium salts andsulfonium salts; oxime sulfonate-based acid generators;diazomethane-based acid generators such as bisalkyl or bisaryl sulfonyldiazomethanes and poly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate-based acid generators; iminosulfonate-based acid generators;and disulfone-based acid generators.

As an onium salt-based acid generator, for example, an acid generatorrepresented by a general formula (b-1) or (b-2) shown below can be used.

(wherein, R¹″ to R³″, R⁵″ and R⁶″ each independently represents an arylgroup or an alkyl group; two of R¹″ to R³″ may mutually be bonded toform a ring together with the sulfur atom; R⁴″ represents a linear,branched or cyclic alkyl group, or a linear, branched or cyclicfluorinated alkyl group; at least one of R¹″ to R³″ represents an arylgroup; and at least one of R⁵″ and R⁶″ represents an aryl group.)

In the general formula (b-1), R¹″ to R³″ each independently representsan aryl group or an alkyl group. Here, two of R¹″ to R³″ in the formula(b-1) may mutually be bonded to form a ring together with the sulfuratom.

Also, at least one of R¹″ to R³″ represents an aryl group. Two or moreof R¹″ to R³″ are preferably aryl groups, and all of R¹″ to R³″ are mostpreferably aryl groups.

There is no particular restriction on the aryl group for R¹″ to R³″. Forexample, the aryl group is an aryl group of 6 to 20 carbon atoms, and apart of or all of hydrogen atoms in the aryl group may be substitutedwith an alkyl group, an alkoxy group, a halogen atom, a hydroxyl groupand the like, or may not be substituted. The aryl group is preferably anaryl group of 6 to 10 carbon atoms because it can be synthesizedinexpensively. Specific examples thereof include a phenyl group and anaphthyl group.

In the aryl group, the alkyl group with which hydrogen atoms may besubstituted is preferably an alkyl group of 1 to 5 carbon atoms, andmost preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, and a tert-butyl group.

In the aryl group, the alkoxy group with which hydrogen atoms may besubstituted is preferably an alkoxy group of 1 to 5 carbon atoms, andmost preferably a methoxy group and an ethoxy group.

In the aryl group, the halogen atom with which hydrogen atoms may besubstituted is preferably a fluorine atom.

There is no restriction on the alkyl groups for R¹″ to R³″. Examplesthereof include a linear, branched or cyclic alkyl group of 1 to 10carbon atoms. The number of carbon atoms is preferably 1 to 5, in termsof excellent resolution. Specific examples include a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, acyclohexyl group, a nonyl group, and a decanyl group. Of these, a methylgroup is preferable, because it excels in resolution, and can besynthesized inexpensively.

Of these, it is most preferable that R¹″ to R³″ each independentlyrepresents a phenyl group or a naphthyl group.

When two of R¹″ to R³″ in the general formula (b-1) may mutually bebonded to form a ring together with the sulfur atom, the ring includingthe sulfur atom preferably forms a 3- to 10-membered ring, and morepreferably forms a 5- to 7-membered ring.

Also, when two of R¹″ to R³″ in the general formula (b-1) may mutuallybe bonded to form a ring together with the sulfur atom, the other of R¹″to R³″ is preferably an aryl group. The aryl group is the same as thosedescribed above in the aryl group for R¹″ to R³″.

R⁴″ represents a linear, branched or cyclic alkyl group, or a linear,branched or cyclic fluorinated alkyl group.

The number of carbon atoms in the linear or branched alkyl group for R⁴″is preferably from 1 to 10, more preferably from 1 to 8, and mostpreferably from 1 to 4.

The cyclic alkyl group for R⁴″ is the same as the cyclic group describedabove in R¹″. The number of carbon atoms in the cyclic alkyl group ofR⁴″ is preferably from 4 to 15, more preferably from 4 to 10, and mostpreferably from 6 to 10.

The number of carbon atoms in the fluorinated alkyl group is preferablyfrom 1 to 10, more preferably from 1 to 8, and most preferably from 1 to4. Furthermore, the fluorination rate of the fluorinated alkyl group(proportion of fluorine atoms in the alkyl group) is preferably within arange from 10 to 100%, more preferably from 50 to 100%, and thosewherein all hydrogen atoms are substituted with fluorine atoms(perfluoroalkyl groups) are particularly preferable, because thestrength of the acid increases.

R⁴″ is most preferably a linear or cyclic alkyl group, or a linear orcyclic fluorinated alkyl group.

In the general formula (b-2), R⁵″ and R⁶″ each independently representsan aryl group or an alkyl group. At least one of R⁵″ and R⁶″ representsan aryl group. Both of R⁵″ and R⁶″ preferably represent aryl groups.

The aryl groups for R⁵″ and R⁶″ are the same as those described above in“aryl group” for R¹″ to R³″.

The alkyl groups for R⁵″ and R⁶″ are the same as those described in“alkyl group” for R¹″ to R³″.

Of these, it is most preferable that both of R⁵″ and R⁶″ be phenylgroups.

R⁴″ in the general formula (b-2) is the same as those described in R⁴″in the general formula (b-1) shown above.

Specific examples of suitable onium salt-based acid generatorsrepresented by formula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-phenyltetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-methoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-ethoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-phenyltetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate.

Also, onium salts in which anionic sites of these onium salts aresubstituted with a methansulfonate, an n-propanesulfonate, ann-butanesulfonate, or an n-octanesulfonate can be used.

Further, an onium salt-based acid generator in which the anionic site inthe general formula (b-1) or (b-2) is substituted with an anionic siterepresented by a general formula (b-3) or (b-4) shown below can also beused. Here, the cationic site is the same as those described in thegeneral formula (b-1) or (b-2).

(wherein, X″ represents an alkylene group of 2 to 6 carbon atoms inwhich at least one hydrogen atom is substituted with a fluorine atom;and Y″ and Z″ each independently represents an alkyl group of 1 to 10carbon atoms in which at least one hydrogen atom is substituted with afluorine atom.)

X″ represents a linear or branched alkylene group in which at least onehydrogen atom is substituted with a fluorine atom. The number of carbonatoms in the alkylene group for X″ is 2 to 6, preferably 3 to 5, andmost preferably 3.

Y″ and Z″ each independently represents a linear or branched alkyl groupin which at least one hydrogen atom is substituted with a fluorine atom.The number of carbon atoms in the alkyl group for Y″ and Z″ is 1 to 10,preferably 1 to 7, and more preferably 1 to 3.

Lower numbers of carbon atoms within the alkylene group for X″ or thealkyl groups for Y″ and Z″ result in better solubility within the resistsolvent, and are consequently preferred.

Furthermore, in the alkylene group for X″ or the alkyl groups for Y″ andZ″, a higher number of hydrogen atoms that have been substituted withfluorine atoms results in increasing the strength of an acid and alsoimproving the transparency relative to high energy light beams of 200 nmor less, or electron beams, and is consequently preferred. Theproportion of fluorine atoms in the alkylene group or alkyl group, thatis, the fluorination rate, is preferably within a range from 70 to 100%,more preferably from 90 to 100%. A perfluoroalkylene group or aperfluoroalkyl group wherein all hydrogen atoms are substituted withfluorine atoms is most preferable.

Further, an onium salt-based acid generator in which the anionic site inthe general formula (b-1) or (b-2) is substituted with an anionic siterepresented by a general formula (b1-12) shown below can also be used.Here, the cationic site is the same as those described in the generalformula (b-1) or (b-2).

R²—O—Y¹—SO₃ ⁻  (b1-12)

(wherein, R² represents a monovalent aromatic organic group; and Y¹represents an alkylene group of 1 to 4 carbon atoms in which hydrogenatoms may be substituted with fluorine atoms.)

In the general formula (b1-12), R² represents a monovalent aromaticorganic group; and Y¹ represents an alkylene group of 1 to 4 carbonatoms in which hydrogen atoms may be substituted with fluorine atoms.

Examples of monovalent aromatic organic groups for R² include arylgroups in which one hydrogen atom has been removed from an aromatichydrocarbon ring, such as a phenyl group, a biphenyl group, a fluorenylgroup, a naphthyl group, an anthryl group, and a phenanthryl group;heteroaryl groups in which a part of the carbon atoms constituting thering(s) of these aryl groups is substituted with hetero atoms such as anoxygen atom, a sulfur atom, and a nitrogen atom; and arylalkyl groupssuch as a benzyl group and a phenethyl group. The number of carbon atomsof the alkyl chain in the arylalkyl group is preferably 1 to 4, morepreferably 1 or 3, and still more preferably 1 to 2.

These aryl groups, heteroaryl groups, and arylalkyl groups may contain asubstituent group such as an alkyl group of 1 to 10 carbon atoms, ahalogenated alkyl group, alkoxy group, a hydroxyl group, and a halogenatom. The number of carbon atoms of the alkyl group or halogenated alkylgroup in the substituent group is preferably 1 to 8, and more preferably1 to 4. Also, the halogenated alkyl group is preferably a fluorinatedalkyl group. Examples of the halogen atom include a fluorine atom, achlorine atom, an iodine atom, and a bromine atom. Of these, a fluorineatom is preferable.

The number of carbon atoms of the monovalent aromatic organic group forR² is preferably 6 to 20, more preferably 6 to 10, and still morepreferably 10.

The monovalent aromatic organic group for R² is preferably an arylalkylgroup such as a benzyl group and a phenethyl group, and more preferablya benzyl group.

Examples of alkylene groups of 1 to 4 carbon atoms for Y¹ which may befluorinated include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF2CF2—, —CF(CF₃)CF2CF2—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CFsCF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—; —CH₂—, —CH2CH2—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

As the alkylene group of 1 to 4 carbon atoms for Y¹ which may befluorinated, it is preferable that the carbon atom bonded with S befluorinated. Examples of such fluorinated alkylene groups include —CF₂—,—CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—;—CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—; —CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and—CH₂CF₂CF₂CF₂—.

Among these, —CF₂CF₂—, —CF₂CF₂CF₂—, and —CH₂CF₂CF₂— are preferable,—CF₂CF₂— and —CF₂CF₂CF₂— are more preferable, and —CF₂CF₂— isparticularly preferable.

Specific examples of the onium salt-based acid generator in which theanionic site is substituted with the anionic site represented by thegeneral formula (b1-12) include compounds represented by generalformulae (b-12-1) to (b-12-18) shown below.

Furthermore, a sulfonium salt that contains a cationic site representedby a general formula (b-5) or (b-6) shown below can be used as an oniumsalt-based acid generator.

(wherein, R⁴¹ to R⁴⁶ each independently represents an alkyl group, anacetyl group, an alkoxy group, a carboxyl group, a hydroxyl group or ahydroxyalkyl group; n₁ to n₅ each independently represents an integer of0 to 3; and n6 represents an integer of 0 to 2.)

The alkyl group for R⁴¹ to R⁴⁶ is preferably an alkyl group of 1 to 5carbon atoms, more preferably a linear or branched alkyl group, andparticularly preferably a methyl group, an ethyl group, a propyl group,an isopropyl group, an n-butyl group, or a tert-butyl group.

The alkoxy group for R⁴¹ to R⁴⁶ is preferably an alkoxy group of 1 to 5carbon atoms, more preferably a linear or branched alkoxy group, andparticularly preferably a methoxy group or an ethoxy group.

The hydroxyalkyl group for R⁴¹ to R⁴⁶ is preferably a group in which oneor more hydrogen atoms in the alkyl group for R⁴¹ to R⁴⁶ are substitutedwith hydrogen atoms, and examples thereof include a hydroxymethyl group,a hydroxyethyl group, and a hydroxypropyl group.

In the case that the symbols n₁ to n₆ to the right of R⁴¹ to R⁴⁶ are aninteger of 2 or more, a multitude of R⁴¹ to R⁴⁶ may each independentlybe the same, or different.

n¹ is preferably 0 to 2, more preferably 0 or 1, and still morepreferably 0.

It is preferable that n₂ and n₃ be each independently 0 or 1, and it ismore preferable that they be 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

There is no particular restriction on an anionic site of a sulfoniumsalt that contains the cationic site represented by the general formula(b-5) or (b-6), and anionic sites of onium salt-based acid generatorswhich have been proposed can be used as the anionic site. Examples ofthe anionic site include a fluorinated alkylsulfonate ion such as theanionic sites (R⁴″SO₃″) of the onium salt-based acid generatorrepresented by the general formula (b-1) or (b-2); and an anionic siterepresented by the general formula (b-3) or (b-4). Of these, afluorinated alkylsulfonate ion is preferable, a fluorinatedalkylsulfonate ion of 1 to 4 carbon atoms is more preferable, and alinear perfluoroalkylsulfonate ion of 1 to 4 carbon atoms isparticularly preferable. Specific examples thereof include atrifluoromethylsulfonate ion, a heptafluoro-n-propylsulfonate ion, and anonafluoro-n-butylsulfonate ion.

In the present specification, the term “oxime sulfonate-based acidgenerator” represents a compound which has at least one of the groupsrepresented by a general formula (B-1) shown below, and has a propertythat generates an acid upon exposure to radiation. These kinds of oximesulfonate-based acid generators are widely used for achemically-amplified resist composition, so any oxime sulfonate-basedacid generator can be used, arbitrarily selected from these.

(In the formula (B-1), R³¹ and R³² each independently represents anorganic group.)

The organic group for R³¹ or R³² is a group containing carbon atoms, andmay further contain atoms other than carbon atoms (for example, ahydrogen atom, an oxygen atom, a nitrogen atom, a sulfur atom and ahalogen atom (a fluorine atom, a chlorine atom and the like)).

The organic group for R³¹ is preferably a linear, branched or cyclicalkyl group or an aryl group. The alkyl group or aryl group may containa substituent group. There is no particular restriction on thesubstituent group, and examples thereof include a fluorine atom, and alinear, branched or cyclic alkyl group of 1 to 6 carbon atoms. Here, theterm “containing a substituent group” represents that a part of or allof hydrogen atoms in the alkyl group or aryl group are substituted withsubstituent groups.

The number of carbon atoms in the alkyl group of R³¹ is preferably 1 to20, more preferably 1 to 10, still more preferably 1 to 8, still morepreferably 1 to 6, and most preferably 1 to 4. The alkyl group for R³¹is particularly preferably an alkyl group which is partially orcompletely halogenated (hereinafter, sometimes referred to as ahalogenated alkyl group). Here, a partially halogenated alkyl grouprepresents an alkyl group in which a part of the hydrogen atoms issubstituted with halogen atoms, and a completely halogenated alkyl grouprepresents an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of the halogen atoms include afluorine atom, a chlorine atom, a bromine atom and an iodine atom. Ofthese, a fluorine atom is preferable. That is, the halogenated alkylgroup is preferably a fluorinated alkyl group.

The number of carbon atoms in the aryl group for R³¹ is preferably 4 to20, more preferably 4 to 10, and most preferably 6 to 10. The aryl groupis particularly preferably an aryl group which is partially orcompletely halogenated. Here, a partially halogenated aryl grouprepresents an aryl group in which a part of the hydrogen atoms issubstituted with halogen atoms, and a completely halogenated aryl grouprepresents an aryl group in which all of the hydrogen atoms aresubstituted with halogen atoms.

R³¹ is particularly preferably an alkyl group of 1 to 4 carbon atomscontaining no substituent group, or a fluorinated alkyl group of 1 to 4carbon atoms.

The organic group for R³² is preferably a linear, branched or cyclicalkyl group, an aryl group, or a cyano group. The alkyl group or thearyl group for R³² is the same as those described above in the alkylgroup or aryl group for R³¹.

R³² is particularly preferably a cyano group, an alkyl group of 1 to 8carbon atoms containing no substituent group, or a fluorinated alkylgroup of 1 to 8 carbon atoms.

The oxime sulfonate-based acid generator is more preferably a compoundrepresented by a general formula (B-2) or (B-3) shown below.

(in the general formula (B-2), R³³ represents a cyano group, an alkylgroup containing no substituent group, or a halogenated alkyl group; R³⁴represents an aryl group; and R³⁵ represents an alkyl group containingno substituent group, or a halogenated alkyl group.)

(in the general formula (B-3), R³⁶ represents a cyano group, an alkylgroup containing no substituent group, or a halogenated alkyl group; R³⁷represents a bivalent or trivalent aromatic hydrocarbon group; R³⁸represents an alkyl group containing no substituent group or ahalogenated alkyl group; and p″ represents an integer of 2 or 3.)

In the general formula (B-2), the number of carbon atoms in the alkylgroup containing no substituent group or the halogenated alkyl group forR³³ is preferably 1 to 10, more preferably 1 to 8, and most preferably 1to 6.

R³³ is preferably a halogenated alkyl group, and more preferably afluorinated alkyl group.

The fluorinated alkyl group for R³³ is preferably a group in which 50%or more of the hydrogen atoms in the alkyl group are fluorinated, morepreferably a group in which 70% or more of the hydrogen atoms in thealkyl group are fluorinated, and still more preferably a group in which90% or more of the hydrogen atoms in the alkyl group are fluorinated.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group; and heteroaryl groups in which apart of the carbon atoms which constitute the rings of these groups aresubstituted with heteroatoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may contain a substituent group such as an alkylgroup of 1 to 10 carbon atoms, a halogenated alkyl group of 1 to 10carbon atoms, and an alkoxy group of 1 to 10 carbon atoms. The number ofcarbon atoms of the alkyl group or halogenated alkyl group in thesubstituent group is preferably 1 to 8, and more preferably 1 to 4.Also, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The number of carbon atoms in the alkyl group containing no substituentgroup or the halogenated alkyl group for R³⁵ is preferably 1 to 10, morepreferably 1 to 8, and most preferably 1 to 6.

R³⁵ is preferably a halogenated alkyl group, and more preferably afluorinated alkyl group.

The fluorinated alkyl group for R³⁵ is preferably a group in which 50%or more of the hydrogen atoms in the alkyl group are fluorinated, morepreferably a group in which 70% or more of the hydrogen atoms in thealkyl group are fluorinated, and still more preferably a group in which90% or more of the hydrogen atoms in the alkyl group are fluorinated,because the strength of the generated acid increases. The fluorinatedalkyl group for R³⁵ is most preferably a completely fluorinated alkylgroup in which 100% of the hydrogen atoms are substituted with fluorineatoms.

In the general formula (B-3), the alkyl group containing no substituentgroup or the halogenated alkyl group for R³⁶ is the same as thosedescribed above in the alkyl group containing no substituent group orthe halogenated alkyl group for R³³.

Examples of the bivalent or trivalent aromatic hydrocarbon group for R³⁷include aryl groups of R³⁴ in which one or two hydrogen atoms arefurther removed.

The alkyl group containing no substituent group or the halogenated alkylgroup for R³⁸ is the same as those described above in the alkyl groupcontaining no substituent group or the halogenated alkyl group for R³⁵.

p″ is preferably 2.

Specific examples of the oxime sulfonate-based acid generator include

-   α-(p-toluenesulfonyloxyimino)-benzylcyanide,-   α-(p-chlorobenzenesulfonyloxyimino)-benzylcyanide,-   α-(4-nitrobenzenesulfonyloxyimino)-benzylcyanide,-   α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzylcyanide,-   α-(benzenesulfonyloxyimino)-4-chlorobenzylcyanide,-   α-(benzenesulfonyloxyimino)-2,4-dichlorobenzylcyanide,-   α-(benzenesulfonyloxyimino)-2,6-dichlorobenzylcyaniide,-   α-(benzenesulfonyloxyimino)-4-methoxybenzylcyanide,-   α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzylcyanide,-   α-(benzenesulfonyloxyimino)-thien-2-ylacetonitrile,-   α-(4-dodecylbenzenesulfonyloxyimino)-benzylcyanide,-   α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,-   α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,-   α-(tosyloxyimino)-4-thienylcyanide,-   α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(methylsulfonyloxyimino)-1-cyclohexenylacetonitnile,-   α-(methylsulfonyloxyimino)-1-cycloheptenylacetonitrile,-   α-(methylsulfonyloxyimino)-1-cyclooctenylacetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-cyclohexylacetonitrile,-   α-(ethylsulfonyloxyimino)-ethylacetonitrile,-   α-(propylsulfonyloxyimino)-propylacetonitrile,-   α-(cyclohexylsulfonyloxyimino)-cyclopentylacetonitrile,-   α-(cyclohexylsulfonyloxyimino)-cyclohexylacetonitrile,-   α-(cyclohexylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile,-   α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile,-   α-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile,-   α-(methylsulfonyloxyimino)-phenylacetonitrile,-   α-(methylsulfonyloxyimino)-p-methoxyphenylacetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-phenylacetonitrile,-   α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenylacetonitrile,-   α-(ethylsulfonyloxyimino)-p-methoxyphenylacetonitrile,-   α-propylsulfonyloxyimino)-p-methylphenylacetonitrile, and-   α-(methylsulfonyloxyimino)-p-bromophenylacetonitrile.

Also, oxime sulfonate-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei9-208554([Formula 18] and [Formula 19] in paragraphs [0012] to [0014]), andInternational Publication WO 2004/074242A2 (Examples 1 to 40 on pages 65to 85) can be preferably used.

Further, suitable examples thereof include the following.

Among the diazomethane-based acid generators, specific examples ofbisalkyl- or bisarylsulfonyldiazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Also, diazomethane-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei11-035551,Japanese Unexamined Patent Application, First Publication No.Hei11-035552, and Japanese Unexamined Patent Application, FirstPublication No. Hei11-035573 can be preferably used.

Examples of the poly(bissulfonyl)diazomethanes include1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, which aredisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei11-322707.

As the component (B), either a single acid generator may be used alone,or a combination of two or more different acid generators may be used.

In the present invention, as the component (B), it is preferable to usean onium salt which contains an anionic site represented by the generalformula (b1-12), it is more preferable to use the compound representedby the formula (b-12-1) to (b-12-18), and it is most preferable to usethe compound represented by the formula (b-12-3).

The amount of the component (B) in the negative resist composition ofthe present invention is preferably within a range from 0.5 to 30 partsby mass, and more preferably from 1 to 10 parts by mass, based on 100parts by mass of the component (A). When the amount is within the range,a pattern can be sufficiently formed. Also, a uniform solution andexcellent storage stability can be obtained, therefore an amount withinthe range is preferable.

<Component (D)>

In the positive resist composition of the present invention, forimproving the resist pattern shape and the post exposure stability ofthe latent image formed by the pattern-wise exposure of the resistlayer, it is possible to add a nitrogen-containing organic compound (D)(hereafter, referred to as component (D)) as an optional component.

Since a multitude of these components (D) have already been proposed,any of these known compounds can be used. Of these, a cyclic amine or analiphatic amine, particularly a secondary aliphatic amine or tertiaryaliphatic amine is preferred. Here, the aliphatic amine represents anamine containing at least one aliphatic group, and the aliphatic grouppreferably has 1 to 12 carbon atoms.

Examples of the aliphatic amine include an amine (alkylamine oralkylalcoholamine) wherein at least one of the hydrogen atoms of NH₃ issubstituted with an alkyl or hydroxyalkyl group having 12 or less carbonatoms. Specific examples thereof include monoalkylamines such asn-hexylanine, n-heptylamine, n-octylamine, n-nonylamine, orn-decylamine; dialkylamines such as diethylamine, di-n-propylamine,di-n-heptylamine, di-n-octylamine, or dicyclohexylamine; trialkylaminessuch as trimethylamine, triethylamine, tri-n-propylamine,tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine,tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine,tri-n-decanylamine, or tri-n-dodecylamine; and alkyl alcoholamines suchas diethanolamine, triethanolamine, diisopropanolamine,triisopropanolamine, di-n-octanolamine, or tri-n-octanolamine. Amongthese amines, alkyl alcoholamines and trialkylamines are preferable, andalkyl alcoholamines are most preferable.

Examples of the cyclic amine include a heterocyclic compound containinga nitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amines include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

These may be used either alone, or in combination of two or moredifferent compounds.

The component (D) is typically used in a quantity within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

<Optional Component> <Component (E)>

In the positive resist composition of the present invention, in order toprevent any deterioration in sensitivity, and improve the resist patternshape and the post exposure stability of the latent image formed by thepattern-wise exposure of the resist layer, at least one compound (E)selected from the group consisting of organic carboxylic acids andphosphorus oxo acids or derivatives thereof (hereinafter, referred to ascomponent (E)) can also be added as an optional component.

Suitable examples of organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids or derivatives thereof includephosphoric acid, phosphonic acid and phosphinic acid. Among these,phosphonic acid is particularly preferable.

Examples of phosphorus oxo acid derivatives include esters in which ahydrogen atom within the above-mentioned oxo acids is substituted with ahydrocarbon group. Examples of the hydrocarbon group include an alkylgroup of 1 to 5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphate esters such asdi-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonate esters suchas dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonic acid,diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic esters suchas phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

As the component (E), an organic carboxylic acid is preferable, andsalicylic acid is particularly preferable.

The component (E) is used in a quantity within a range from 0.01 to 5.0parts by weight, relative to 100 parts by weight of the component (A).

In the positive resist composition of the present invention, if desired,additives having miscibility, for example, additive resins for improvingperformance of a resist film, surfactants for improving coatability,dissolution inhibitors, plasticizers, stabilizers, colorants,antihalation agents, and dyes can be appropriately added.

<Component (S)>

The positive resist composition of the present invention can be preparedby dissolving materials in an organic solvent (hereinafter, sometimesreferred to as component (S)).

The component (S) may be an organic solvent which can dissolve therespective components used in the present invention to give a uniformsolution, and one or more kinds of organic solvents can be used,appropriately selected from those which have been conventionally knownas a solvent for a chemically-amplified resist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone,methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols such asethylene glycol, diethylene glycol, propylene glycol, dipropyleneglycol; derivatives of the polyhydric alcohols, including compoundshaving ester bonds such as ethylene glycol monoacetate, diethyleneglycol monoacetate, propylene glycol monoacetate and dipropylene glycolmonoacetate, and compounds having ether bonds such as monoalkyl ethers(for example, monomethyl ether, monoethyl ether, monopropyl ether andmonobutyl ether) and monophenyl ether of the above polyhydric alcoholsor the above compounds having ester bonds (of these, propylene glycolmonomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether(PGME) are preferable); cyclic ethers such as dioxane; esters such asmethyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butylacetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate,ethyl ethoxypropionate; and aromatic organic solvents such as anisole,ethylbenzyl ether, cresylmethyl ether, diphenyl ether, dibenzyl ether,phenetole, butylphenyl ether, ethylbenzene, diethylbenzene,pentylbenzene, isopropylbenzene, toluene, xylene, cymene, andmesitylene.

These organic solvents may be used either alone, or as a mixed solventof two or more different solvents.

Of these, propylene glycol monomethyl ether acetate (PGMEA), propyleneglycol monomethyl ether (PGME) and EL are preferable.

Also, a mixed solvent obtained by mixing PGMEA and a polar solvent ispreferable. The mixing ratio (mass ratio) of PGMEA to the polar solventmay be appropriately decided taking account of compatibility, and ispreferably adjusted within a range from 1:9 to 9:1, and more preferablyfrom 2:8 to 8:2.

More specifically, in the case of using EL as the polar solvent, themass ratio PGMEA:EL is preferably from 1:9 to 9:1, and more preferablyfrom 2:8 to 8:2. Furthermore, in those cases of using PGME as the polarsolvent, the mass ratio PGME:PGME is preferably from 1:9 to 9:1, morepreferably 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Furthermore, as the component (S), mixed solvents of at least one ofPGMEA and EL with γ-butyrolactone are also preferred. In such cases, themass ratio of the former and latter components in the mixed solvents ispreferably within a range from 70:30 to 95:5.

There is no particular restriction on the quantity of the component (S),and the quantity should be set in accordance with the required coatingfilm thickness within a concentration that enables favorable applicationof the solution to a substrate or the like. Typically, the quantity isset so that the solid fraction concentration within the resistcomposition falls within a range from 2 to 20% by weight, and still morepreferably from 5 to 15% by weight.

Since the positive resist composition of the present invention includesthe polymer compound (A1) which contains the structural units (a0) and(a1) as the component (A), it can form a resist film with excellentresolution and high sensitivity, as compared with conventional positiveresist compositions. Although the reasons why these effects can beobtained are not clear, the following reasons can be speculated. Thatis, since the structural unit (a0) has a polycyclic aliphatichydrocarbon group with a hydrophobic and bulky structure and a sultonering at once, the polymer compound (A1) containing the structural unit(a0) has excellent hydrolyzability and excellent solubility afterhydrolysis, in spite of the high chemical stability. Therefore, it isspeculated that, in the case that the polymer compound (A1) is used as amaterial for a positive resist composition, the solubility at theexposed portions is improved in the alkali developing treatment, andthus the resolution and sensitivity can be enhanced.

Therefore, in the case of using the positive resist composition of thepresent invention, a resist pattern with excellent mask reproducibilityand extremely excellent pattern shape can be formed with less exposureamount, as compared with the case of using a resist compositioncontaining a polycyclic aliphatic hydrocarbon group which has a lactonering at once, conventionally used for an ArF resist For example, in thecase that a contact hole pattern is formed on a resist film formed byusing the positive resist composition of the present invention, a resistpattern in which each hole has excellent circularity can be formed.

<<Method of Forming Resist Pattern>>

A method of forming a resist pattern of the present invention includesthe steps of forming a resist film on a substrate using the positiveresist composition described above, exposing the resist film, anddeveloping the resist film to form a resist pattern.

The method of forming a resist pattern of the present invention can beperformed, for example, in the following manner.

Namely, the positive resist composition described above is first appliedto a substrate using a spinner or the like, a prebake is then conductedunder temperature conditions of 80 to 150° C. for 40 to 120 seconds,preferably for 60 to 90 seconds, followed by selective exposure of thethus obtained film with an ArF exposure apparatus or the like, byirradiating ArF excimer laser light through a desired mask pattern, andthen PEB (post exposure baking) is conducted under temperatureconditions of 80 to 150° C. for 40 to 120 seconds, preferably for 60 to90 seconds. Subsequently, a developing treatment is conducted using analkali developing solution such as a 0.1 to 10% by mass aqueous solutionof tetramethylammonium hydroxide (TMAH), preferably followed by rinsingwith pure water, and drying. Also, according to circumstances, a baketreatment (post bake) may be conducted after the above developingtreatment. In this manner, a resist pattern that is faithful to the maskpattern can be obtained.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having prescribed wiring patterns formedthereon can be exemplified. Specific examples thereof include a siliconwafer; a substrate made of a metal such as copper, chromium, iron andaluminum; and a substrate made of glass. As materials for the wiringpattern, for example, copper, aluminum, nickel and gold can be used.

Further, as the substrate, any one of the above-exemplified substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic anti-reflection film(inorganic BARC) can be exemplified. As the organic film, an organicanti-reflection film (organic BARC) can be exemplified.

There is no particular restriction on the wavelength used for theexposure, and the exposure can be conducted using radiation such as ArFexcimer lasers, KrF excimer lasers, F2 excimer lasers, extremeultraviolet rays (EUV), vacuum ultraviolet rays (VUV), electron beams(EB), X-rays, and soft X-rays. The positive resist composition iseffective for use with KrF excimer lasers, ArF excimer lasers, electronbeam (EB), or extreme ultra violet (EUV), and particularly effective foruse with EB.

EXAMPLES

Next, the present invention will be described in more detail withreference to examples, but the scope of the present invention is notlimited to the following examples.

<Synthesis of Polymer Compound (A)-1>

2.50 g of the compound represented by the above formula (1), 4.01 g ofthe compound represented by the above formula (2), and 1.08 g of thecompound represented by the above formula (3) were dissolved in 30.33 gof methyl ethyl ketone. 1.53 mmol of V-601 (manufactured by Wako PureChemical Industries, Ltd.) serving as a polymerization initiator wasadded into the solution thus obtained, thereby being dissolved. Thesolution thus obtained was dropped in 12.64 g of methyl ethyl ketonewhich was heated at 75° C., under a nitrogen atmosphere for 6 hours.After the dropping treatment was finished, the reaction solution wasstirred on heating for 1 hour, and then cooled down at room temperature.

Cooled reaction solution was dropped in a large amount of a mixturesolvent of MeOH/H₂O, and the treatment of separating the polymercompound was repeatedly conducted twice. The polymer compound thusobtained was dried under reduced pressure at room temperature, therebyobtaining a white powder.

The carbon 13 nuclear magnetic resonance spectrum (600 MHz_(—) ¹³C-NMR)of the polymer compound was measured. As a result, the proportion (molarratio) of structural units in the polymer compound was“1/m/n=42.6/41.4/16.0”. Also, the weight average molecular weight (Mw)(the polystyrene equivalent value determined by gel permeationchromatography (GPC)) was 7,300, and the dispersion degree was 1.90.From the results, it was found that the compound obtained was a polymercompound (A)-1 shown below.

<Synthesis of Polymer Compound (A)-2>

6.67 g of the compound represented by the above formula (1′), 12.40 g ofthe 10 compound represented by the above formula (2), and 4.44 g of thecompound represented by the above formula (3) were dissolved in 94.04 gof methyl ethyl ketone. 3.00 mmol of V-601 (manufactured by Wako PureChemical Industries, Ltd.) serving as a polymerization initiator wasadded into the solution thus obtained, thereby being dissolved.

The solution thus obtained was dropped in 3.18 g of methyl ethyl ketonewhich was heated at 75° C., under a nitrogen atmosphere for 6 hours.After the dropping treatment was finished, the reaction solution wasstirred on heating for 1 hour, and then cooled down at room temperature.

Cooled reaction solution was dropped in a large amount of a mixturesolvent of MeOH/H₂O, and the treatment of separating the polymercompound was repeatedly conducted twice. The polymer compound thusobtained was dried under reduced pressure at room temperature, therebyobtaining a white powder.

The carbon 13 nuclear magnetic resonance spectrum (600 MHz_(—) ¹³C-NMR)of the polymer compound was measured. As a result, the proportion (molarratio) of structural units in the polymer compound was“1/m/n=38.7/39.2/22.1”. Also, the weight average molecular weight (Mw)(the polystyrene equivalent value determined by gel permeationchromatography (GPC)) was 7,100, and the dispersion degree was 1.56.From the results, it was found that the compound obtained was a polymercompound (A)-2 shown below.

<Preparation of Positive Resist Composition>

The components shown in Table 1 were mixed and dissolved, therebyproviding a positive resist composition solution.

TABLE 1 Component Component Component (A) (B) (D) Component (S) Example1 (A)-1 (B)-1 (D)-1 (S)-1 [100] [4.87] [0.1] [2000] Comparative (A)-2(B)-1 (D)-1 (S)-1 Example 1 [100] [4.87] [0.1] [2000]

In Table 1, the abbreviations represent the following meanings. Also,the values within the brackets [ ] represent the blending amount (partsby weight).

(A)-1: polymer compound represented by the formula (A)-1

(A)-2: polymer compound represented by the formula (A)-2

(B)-1: acid generator represented by the general formula (b-12-3)

(D)-1: tri-n-pentylamine.

(S)-1: a mixture solvent of PGMEA/PGME=6/4 (mass ratio).

<Evaluation of Lithography Properties>

Resist patterns were formed using the positive resist composition thusobtained, and the following lithography properties were evaluated.

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied onto an 8-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 77 nm. Then, the positive resist composition solutionobtained above was applied onto the anti-reflection film using aspinner, and was then prebaked (PAB) on a hotplate at 100° C. for 60seconds and dried, thereby forming a resist film having a film thicknessof 120 nm.

Subsequently, targeting 130 nm of aperture and 260 nm of pitch, theobtained resist layer was selectively exposed by an ArF excimer laser(193 nm), using an ArF exposure apparatus “NSR-S306” (manufactured byNikon; numerical aperture (NA)=0.60, 2/3 annual illumination) through amask pattern (6% half tone). Thereafter, a post exposure baking (PEB)treatment was conducted at 95° C. for 60 seconds, followed by adevelopment treatment for 30 seconds at 23° C. in a 2.38% by weightaqueous solution of tetramethylammonium hydroxide (TMAH), rinsing withpure water for 30 seconds, and drying by shaking.

As a result, the contact hole pattern (C/H pattern) was formed on eachresist film, with approximately 130 nm of hole diameter (CD) and atregular intervals (260 nm of pitch). Particularly, the resist filmformed by using the polymer compound (A)-1 had small variations in holediameters, and the circularity was extremely excellent, as compared withthe resist film formed by using the polymer compound (A)-2.

Also, the optimum exposure (sensitivity: Eop, mJ/cm²) for a C/H patternwith a hole diameter of 130 nm and pitch of 260 nm was determined. As aresult, the optimum exposure in the resist film formed by using thepolymer compound (A)-1 was 52.4 mJ/cm², and the optimum exposure in theresist film formed by using the polymer compound (A)-2 was 59.5 mJ/cm².

From the above results, it is clear that a resist pattern with excellentresolution and sensitivity, and with particularly excellent circularityin the formation of a C/H pattern can be formed by using a positiveresist composition which includes the polymer compound (A1) containingthe structural unit (a0) represented by the general formula (a0-1) andthe structural unit (a1) derived from an acrylate ester which containsan acid dissociable, dissolution inhibiting group.

INDUSTRIAL APPLICABILITY

The present invention provides a polymer compound with an excellentresolution and sensitivity, a positive resist composition which includesthe polymer compound; and a method of forming a resist pattern.

1. A positive resist composition, comprising a resin component (A) whichdisplays increased solubility in an alkali developing solution underaction of acid; and an acid generator component (B) which generates anacid upon exposure, wherein the resin component (A) comprises a polymercompound (A1) which comprises a structural unit (a0) represented by ageneral formula (a0-1) shown below, and a structural unit (a1) derivedfrom an acrylate ester containing an acid dissociable, dissolutioninhibiting group:

(in the formula (a0-1), R represents a hydrogen atom, a lower alkylgroup, or a halogenated lower alkyl group; two of R′ each independentlyrepresents a hydrogen atom, a lower alkyl group, or an alkoxy group of 1to 5 carbon atoms; and X represents an alkylene group of 1 to 5 carbonatoms, an oxygen atom, or a sulfur atom.).
 2. The positive resistcomposition according to claim 1, further comprising a structural unit(a3) derived from an acrylate ester which has a polar group-containingaliphatic hydrocarbon group.
 3. The positive resist compositionaccording to claim 1, further comprising a nitrogen-containing organiccompound (D).
 4. A method of forming a resist pattern, comprising:forming a resist film on a substrate using the positive resistcomposition described in any one of claims 1 to 3; exposing the resistfilm; and alkali-developing the resist film to form a resist pattern. 5.A polymer compound, comprising a structural unit (a0) represented by astructural unit (a0-1) shown below, and a structural unit (a1) derivedfrom an acrylate ester containing an acid dissociable, dissolutioninhibiting group:

(in the formula (a0-1), R represents a hydrogen atom, a lower alkylgroup, or a halogenated lower alkyl group; two of R′ each independentlyrepresents a hydrogen atom, a lower alkyl group, or an alkoxy group of 1to 5 carbon atoms; and X represents an alkylene group of 1 to 5 carbonatoms, an oxygen atom, or a sulfur atom.).
 6. The polymer compoundaccording to claim 5, further comprising a structural unit derived froman acrylate ester which has a polar-group containing an aliphatichydrocarbon group.